After hydrocarbons have been removed from the ground, the fluid stream (e.g., crude oil, natural gas) is transported from place-to-place via pipelines. It is desirable to know with accuracy the amount of fluid flowing in the stream, and particular accuracy is demanded when the fluid is changing hands, or “custody transfer.” Even where custody transfer is not taking place, however, measurement accuracy is desirable, and in these situations flow meters may be used.
Ultrasonic flow meters are one type of flow meter that may be used to measure the amount of fluid flowing in a pipeline. In an ultrasonic flow meter, ultrasonic signals are sent back and forth across the fluid stream to be measured, and based on various characteristics of the ultrasonic signals, a fluid flow may be calculated. The accuracy of an ultrasonic flow meter is subject various conditions that affect the calibration and/or operation of the meter. For example, accumulation of contaminants in the pipeline, flow restrictions, and/or differences in calibration versus operation environment may affect flow meter accuracy.
Accordingly, effective techniques for monitoring conditions related to flow meter accuracy are desirable.